It is known to pack products for infusions, such as tea, chamomile and the like, inside filter-bags. Recently there has increased and gained favour among the consumers a product called "filtro-fiore" in Italian (flower-filter in English), consisting of almost integral chamomile flowers which are packed, as much as possible intact to merit such a name.
This product is per se scarcely slidable, extremely fragile and dishomogeneous, as the various parts which compose a chamomile flower, and comprise the product, have physical characteristics, particle size and specific weight which are considerably different from each other.
Up to now a batcher designed by the same applicant has been adopted for the dosed filling of filter-bags in a packing machine of known type, which batcher proved to be relatively sufficient as far as both the quality of the product and the protection of the physical aspect thereof are concerned. The batcher is of the volumetric type, as it is not conceivable to employ batchers on a ponderal basis, each dosing being about 2 g in weight and the relative weighing having to occur at a rhythm of about 100 times per minute, with minimum deviations percent and therefore negligible ones in absolute value.
In the known batchers it was possible to overcome the problem of unreliable batcher filling, thus avoiding the so called "bridges" of material, due to both the dishomogeneity of the product and the dimensions thereof, and taken into account that a bud of chamomile with its stalk can have an overall length of 3.div.3.5 cm, thus involving, as a result of its arrangement, problems in filling the batcher with more product due to blockage of the passage. The problem was solved by adopting a mobile batching chamber inside which the filling takes place by a free fall of the product and a successive compression thereof by means of a pad actuated by a pneumatic cylinder. Such a batching chamber is formed in a mobile plate and is closed at its bottom by a small door which is adjustable in height to change the dose volume and can be opened each time for discharging the product. The batcher consists of both said mobile plate and a fixed supporting one which has a through hole with the same size of the batching chamber. When the latter is aligned with said through hole of the fixed plate, which hole is arranged coaxially with the vertical of a loading conduit through which said compressing pad slides, there occurs the filling of the batching chamber. The following stroke of the mobile plate, causes the clean cut of a core of product, due to the sliding of the upper edges of the batching chamber against the lower surface of the fixed plate above, while the upper surface of the mobile plate prevents the product from falling from both the loading conduit and the through hole of the fixed plate. The small door opens near the end of a stroke of the mobile plate, with consequent falling down of dosed product in a filter-bag below, which is submitted by the packing machine. The vertical loading conduit communicates with a hopper, which is continuously fed by a reservoir through a screw-feeder which, by drawing therefrom, raises the product up to the upper edge of said hopper, while anyhow needing additional means such as spirals at its sides, to overcome the difficulties of drawing due to the scarce smoothness of the product, but with the consequence of some damages to the integrity of the product itself.
In spite of the merits of the above briefly described device, the most considerable limit thereof remains a limited productivity, as it has a filling rate of about 100 filter-bags per minute. It has been found that, for rates higher than 110 cycles per minute, the gravity fall just after the opening of the small door with a slight advance with respect to the forming of a filter-bag, involves different fall times, mainly due to the dishomogeneity of each component. Thus it is not possible to increase the working rate of the batcher to have it coincident with the working rate of faster packing machines which theoretically could ensure a higher productivity.
Also the experimented hypothesis of employing a carousel of small containers placed between the batchers and a single packing station was found to be not practicable as, by using N intermediate containers, the batchers rate would positively be 1/N of the machine rate, but the transfer of the dose to the carousel and therefrom to a filling area, would have to take place in a very short time, less than 1/(N.times.100). The limit seems to be mainly due to the free fall of the product.
Thus an improved batching device has been conceived and forms the object of the present invention, which does not show the above mentioned drawbacks, as it has a filling rate which is, on the whole, higher and adequate to the working rate of already existing packing machines which are suitable to work at the same time, with high productivity, at many stations for filter-bags filling, without proportionally increasing the batcher working rate.